Fix potential crash when fullscreen view unmaps
Fix potential crash when fullscreen view unmaps

It happened when a view is a grandchild or deeper of the workspace, is
fullscreen, and unmaps. The workspace would not be included in the
transaction and its pointer to the fullscreen view was left dangling.

1ace/sway,1ace/sway,SirCmpwn/sway,ascent12/sway,ascent12/sway,taiyu-len/sway,1ace/sway,ascent12/sway,taiyu-len/sway,taiyu-len/sway